Radiant tube and convection oven

Abstract

An oven for heating a coating on a substrate, such as a painted vehicle body, including a first zone having radiant tubes and shields above the tubes and a second zone including side heat chambers having nozzles directing heated air onto a coated substrate and a hold zone. The radiant tubes may include a first linear portion extending through the oven and return loop beneath the substrate to conserve energy and sill ducts directing heated air against the underside of the vehicle body. The temperature is controlled by sensors contacting the radiant tubes and a proportional integral control system.

Description

RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Patent Application Ser. No. 60 / 513,748 filed Oct. 23, 2003.BACKGROUND OF THE INVENTION[0002]At present, paint and other coatings are baked or cured in a radiant oven, wherein the walls and / or floor are heated by combustion burners. In a typical automotive application, the painted vehicle body is conveyed through the radiant oven and the opposed side walls and generally the floor of the oven are heated by combustion burners which direct hot air into rectangular enclosures defining the side and bottom walls of the oven. This method of heating requires flame sensors to avoid a potential explosion which automatically turn off the flow of combustible gas to the burners in the event that the burner fails and combustible gas is directed into the enclosures thus shutting down the oven. The enclosures must then be purged of combustible gas before restarting the burners and restarting the oven. As a safety feature,...

AI Technical Summary

Benefits of technology

[0006]In one preferred embodiment, the radiant tube or pipe is positioned along one side wall of the oven adjacent to but spaced from the side wall and the radiant tube is then turned or bent 180° at the end of the radiant tube with an additional length of tube or pass running parallel to the direction of the conveyor travel, preferably beneath the substrate, such as the vehicle body. Utilization of this second run of pipe allows greater efficiency and utilization of the heat value of the fuel burned and improved distribution of the heat. The second length of radiant tube is preferably located near the floor of the oven and below the level of the conveyor. This allows for transfer of heat energy to the thicker metal parts of the vehicle body on the underside of the vehicle body. The second length of radiant tube may have the same diameter as the first length of tube, but may also have a larger diameter to reduce pressure loss and increase heat transfer. However, a smaller diameter for the second length of tube may be advantageous in fitting under the vehicle body, if space is limited.

[0009]In the radiant bring-up section or zone, radiant tubes extend through the radiant bring-up zone preferably adjacent an intersection between the side wall and the bottom wall of the oven having a generally horizontal metal shield located above the radiant tube heaters to prevent overheating of the light metal parts of the vehicle body located above the radiant tubes. In a more preferred embodiment, the radiant bring-up zone also includes sill ducts located below the vehicle body in the vicinity of the door sills which may include a series or nozzles or holes directing air at the underside of the vehicle. The radiant tube heaters preferably receive pulse-fired gas burners which are heated to a surface temperature of between 400° F. and 1000° F. by the pulse-fired gas burners and the radiant tube heaters preferably have a wall thickness to prevent explosion.

Problems solved by technology

As will be understood by those skilled in this art, restarting a paint oven after shut down because of a failure of either the burner or a flame sensor requires time and thus considerable expense, but safety precautions must be maintained to avoid a hazardous condition.

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